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In this study, the application of the core‐shell Fe3O4@SiO2 nano‐catalysts for fenton‐like degradation of malachite green dye has been presented. The nano‐catalysts were prepared using a combination of solvothermal and sol‐gel techniques and characterized using XRD, FTIR, SEM/EDX, TEM and VSM techniques. The effects of various reaction parameters on the degradation of malachite green dye using the prepared nano‐catalysts were investigated. The optimal condition for pH, catalyst dosage and H2O2 amount were found to be at 6.7, 15 mg and 50 μL, respectively. Under the optimized conditions, a degradation efficiency of 96.18 % for malachite green dye was achieved using the catalyst within 30 minutes at 303 K with a pseudo first order rate constant of 0.1102 min−1. The plausible mechanism for MG degradation was determined to be the combination of adsorption and simultaneous decomposition via formation of hydroxyl radicals. The performance of the nano‐catalyst was compared with other fenton‐like catalysts reported in the literature. Finally, the magnetic properties of the Fe3O4@SiO2 catalysts was utilized for its successful recovery and application in multiple degradation cycles. [ABSTRACT FROM AUTHOR]

Palm oil mill effluent (POME) is a highly polluted agro-industrial wastewater. The CO2 in industrial flue gas requires treatment before it can be discharged into the environment. Utilizing microalgae as the agent to treat wastewater and industrial flue gas is a waste-to-wealth approach. The resulting biomass can be commercialized in the form of valuable products. Chlorella sp. is a microalgal species that can tolerate the pollutant load and has been proven to be a suitable species for CO2 fixation. In this study, Chlorella sp. was cultivated in POME with the aim of reducing the pollutants in the POME and simultaneously capturing CO2. The optimization of the operational conditions of this microalgae-based treatment system was carried out using the response surface methodology (RSM) face centered-central composite design (FC-CCD). Operational factors include the air concentration of CO2 (10-25% v/v), the inlet gas flow rate of 500-2000 mL min−1, and initial inoculum concentration (10-30% v/v) of Chlorella sp. cultivated in POME. The target deliverables include the maximum amount of CO2 fixed by Chlorella sp. and the total nitrogen (TN) reduction as indicators of pollutant reduction by this treatment system. We found that a limited supply of CO2 caused growth limitation, while excess CO2 resulted in acid production that triggered microalgae growth inhibition. The optimum operational conditions were 10% v/v CO2, 1670 mL min−1 aeration rate, and 24.8% v/v inoculum concentration, predicted to simultaneously fix CO2 at 0.12 g of CO2 L−1 day−1 and reduce 80.9% TN, respectively. [ABSTRACT FROM AUTHOR]

Mixed Cu and Mg oxides on nitrogen-rich activated carbon (AC) from Nypha fruticans biomass were characterized and their CO adsorption performance was measured. Highly dispersed CuO and MgO nanoparticles on AC was obtained using an ultrasonic-assisted impregnation method. The optimum adsorbent is 5%CuO-25%MgO/AC having good surface properties of high surface area, pores volume and low particles agglomeration. The higher content of MgO of 5%CuO-25%MgO/AC adsorbent contributes to less metal carbide formation which increases their porosity, surface area and surface basicity. XPS analysis showed some amount of nitrogen content on the surface of the adsorbent which increased their surface basicity towards selective CO adsorption. The presence of moisture accelerated the CO chemisorption to form a hydroxyl layer on the surfaces. The 5%CuO-25%MgO/AC adsorbent successfully adsorbed CO via physisorption and chemisorption of 14.8 and 36.2 wt%, respectively. It was significantly higher than fresh AC with better selectivity to CO. [ABSTRACT FROM AUTHOR]

In this study, the performance enhancement of polyvinylidene fluoride (PVDF) polymer as one of the most hydrophobic membrane material, blended with zinc oxide (ZnO) and zinc oxide/reduced graphene oxide (ZnO/rGO) was investigated. ZnO/rGO composites which acted as inorganic filler were synthesized via a facile precipitation method using zinc nitrate (Zn(NO3) 2) as zinc precursor and sodium hydroxide (NaOH) as reducing agent. The synthesized ZnO/rGO composites with various Zn loadings were analyzed in terms of particles size and surface charge. The composites with highest surface charge and smallest particles size were then selected for PVDF membrane fabrication. The membranes were produced via immersion-precipitation method and they were characterized by water permeation test, contact angle, morphology, bovine serum albumin (BSA) rejection, flux recovery and antibacterial activity. Based on the findings, ZnO/rGO composites gave the most hydrophilic effect to the PVDF membranes, resulted in 61% of permeation flux increment in comparison with neat PVDF membranes. Simultaneously, the ZnO/rGO mixed matrix membranes (MMMs) showed the highest BSA rejection of 32% and flux recovery ratio of 48%, implying the improvement of the membranes’ fouling resistance. Besides, there was no release of Zn element in permeate of ZnO/rGO MMMs which implied the strong bonding between ZnO/rGO composite with PVDF membranes. In addition, the superior antibacterial property of ZnO/rGO MMMs showed great potential in biofouling mitigation. Hence, the utilization of ZnO/rGO MMMs was highly recommended in various applications involving fouling and biofouling issues. [ABSTRACT FROM AUTHOR]

In this study, the optical properties of a TiO2 photocatalyst were enhanced with various impregnations of Er3+ and Ni2+ separately, using the impregnation method as photocatalysts for the direct solar photolysis degradation of chloroxylenol. The synthesized Er3+/TiO2 and Ni2+/TiO2 catalysts were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), metal mapping, and ultraviolet visible (UV–Vis) spectroscopy. The results showed that the Er3+/TiO2 and Ni2+/TiO2 nano-particles have the same structures of TiO2 nano-particles with little difference in particle size. The Er3+ and Ni2+ ions were well-distributed on the TiO2 surface, and it was found that the maximum band gap decreased from 3.13 eV for intrinsic TiO2 to 2.63 eV at 1.8 wt % Er3+/TiO2 and to 2.47 eV at 0.6 wt % for Ni2+/TiO2. The initial concentration of chloroxylenol, catalyst loading, and pH of the solution are the most important factors affecting the solar photocatalytic degradation efficiency that were optimized using Design Expert software (version 6.0.10, Minneapolis, MN, USA, 2003). The results showed that the optimal conditions for chloroxylenol degradation include a pH of 4, TiO2 loading at 3 g/L, and a chloroxylenol concentration of 50 mg/L. These conditions resulted in a degradation efficiency of 90.40% after 60 min of direct solar irradiation, wherein the solar energy recorded during a clear sunny day is 1000 W/m2. However, some experiments were conducted on a semi-cloudy day to cover all weather stated and to study the degradation kinetics. During semi-cloudy day experiments, using Er3+/TiO2 and Ni2+/TiO2 with a solar irradiation activity of 600 W/m2 for a 60 min exposure at optimal conditions increased the degradation efficiency from 68.28% for intrinsic TiO2 to 82.38% for Er3+/TiO2 and 80.70% for Ni2+/TiO2. [ABSTRACT FROM AUTHOR]

Incorporation of nanoparticles in membranes has recently been reported to lead to enhancement of the membrane performance for various applications. In this study, ZnO nanoparticles were synthesized via sol–gel method using zinc acetate and oxalic acid as starting materials. However, the influence of additive, in this case ethylene glycol (EG), on the size of ZnO nanoparticles produced was investigated. All diffraction peaks of XRD patterns indicated the wurtzite structure and the hexagonal phase of ZnO nanoparticles. Uniform spherical particle sizes with lower sizes and reduced agglomeration were observed when EG was used under the same experimental conditions. The particle size was found in the range of 20–30 nm when EG was used as compared to those without EG, which was between 50–60 nm. Dispersion property of the ZnO NPs was further verified by zetasizer analysis. Subsequent incorporation of the smaller size ZnO nanoparticles in membranes has shown improvement in the characteristics and performance of the membranes. Membranes incorporated with ZnO showed improved hydrophilicity and enhancement of membrane performance in terms of permeability, porosity, and rejection ability. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) has excellent potential to be used in water and wastewater treatment, either as a photocatalyst or in membrane incorporation. In this work, the synthesis of smaller ZnO NPs through a sol-gel approach was enhanced by applying Taguchi design. Recent work on the synthesis of ZnO NPs was optimised to ensure relatively smaller sized particles were obtained. Several parameters of the synthesis process, such as molar ratio of starting materials, molar concentration and calcination temperature, were selected as they have the dominant effects on the particle size of ZnO NPs. Each of these factors was studied at three levels. Various analyses such as ANOVA, model adequacy check and numerical optimisation were performed to validate the predicted optimal model. As a result, the optimum conditions were estimated at a molar ratio of 50:50, an oxalic acid molar concentration of 0.1 M and a calcination temperature of 400 °C. Experiments were performed to validate the model at the selected conditions and the particle size was around 20 ± 2 nm according to XRD analysis, which was in good agreement with the predicted size of 19.8 nm. In addition, the actual size of the synthesised NPs was confirmed by TEM analysis, with the average size of 13 ± 5 nm. Hence, the Taguchi design was an essential tool in the optimisation of ZnO NP synthesis process with fewer experimental runs and relatively low cost approach. [ABSTRACT FROM AUTHOR]

Abstract: The optical properties of a ZnO photocatalyst were enhanced with various dopant concentrations of Fe3+. Doped ZnO nanoparticles were synthesized via a sol–gel method without the use of capping agents or surfactants and was then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet–visible (UV–Vis) spectroscopy. The results showed that ZnO has a wurtzite, hexagonal structure and that the Fe3+ ions were well incorporated into the ZnO crystal lattice. As the Fe3+ concentration increased from 0.25wt.% to 1wt.%, the crystal size decreased in comparison with the undoped ZnO. The spectral absorption shifts of the visible light region (red shift) and the band gap decreases for each Fe–ZnO sample were investigated. The photocatalytic activities of the ZnO and Fe–ZnO samples were evaluated based on the degradation of 2-chlorophenol in aqueous solution under solar radiation. The samples with a small concentration of Fe3+ ions showed enhanced photocatalytic activity with an optimal maximum performance at 0.5wt.%. The results indicated that toxicity removal of 2-chlorophenol at same line of degradation efficiency. Small crystallite size and low band gap were attributed to high activities of Fe–ZnO samples under various concentrations of Fe3+ ions compared to undoped ZnO. [Copyright &y& Elsevier]

In this study, the photocatalytic degradation of toxic pollutant (2-chlorophenol) in the presence of ZnO nanoparticles (ZnO NPs) was investigated under solar radiation. The three main factors, namely pH of solution, solar intensity and calcination temperature, were selected in order to examine their effects on the efficiency of the degradation process. The response surface methodology (RSM) technique based on D-optimal design was applied to optimise the process. ANOVA analysis showed that solar intensity and calcination temperature were the two significant factors for degradation efficiency. The optimum conditions in the model were solar intensity at 19.8 W/m 2 , calcination temperature at 404 °C and pH of 6.0. The maximum degradation efficiency was predicted to be 90.5% which was in good agreement with the actual experimental value of 93.5%. The fit of the D-optimal design correlated very well with the experimental results with higher values of R 2 and R 2 adj correlation coefficients of 0.9847 and 0.9676, respectively. The intermediate mechanism behaviour of the 2-chlorophenol degradation process was determined by gas chromatography-mass spectrometry (GC-MS). The results confirmed that 2-chlorophenol was converted to acetic acid, a non-toxic compound.